The Applicant has developed the Netpage system discussed in detail below. As the invention is particularly well suited to sensing devices for this system, it will be described in a Netpage context. However, it will be appreciated that force sensors have uses in many applications. In particular, hand-held optical sensors have broad ranging applications in many different fields and the invention is not limited to its use within the Netpage system or, indeed, optical sensing devices.
The Netpage system involves the interaction between a user and a computer network (or stand alone computer) via a pen and paper based interface. The ‘pen’ is an electronic stylus with a marking or non-marking nib and an optical sensor for reading a pattern of coded data on the paper (or other surface).
One of the primary features of the Netpage pen is its ability to ‘click’ on interactive elements on a Netpage in the same way a mouse can click on screen-based interactive elements (e.g. hyperlinks and so on). However, with a Netpage pen, the user simply puts the nib on the interactive element in order to click on it. The optical sensor identifies the element via its unique page and location ID while a force sensor registers a ‘pen down’ condition when the nib is pressed against the page. Registering ‘pen down’ and ‘pen up’ is also fundamental to capturing the user's handwriting on Netpage input fields. Non-binary force signals are also captured for reproducing hand-drawn strokes with varying force-related width and opacity. Force variation can also be used as one of the dimensions examined during signature verification.
The force sensor is required to sense accurately relatively light forces (such as the force of handwriting on a nib). It should also require minimal power and be suitable for incorporation into a handheld sensing device.